The invention relates to coordinating the actuation of secondary units in a motor vehicle. In particular, the invention relates to a control unit and to a process for coordinating the actuation of at least one secondary unit of the motor vehicle, which can be driven by a principal unit, as well as to a secondary unit for a motor vehicle which can be driven by the principal unit of the motor vehicle.
As a result of the rising number of secondary units and the increasing networking of systems in motor vehicles, it has become necessary to develop a so-called torque manager, which coordinates the various torque demands made on the internal-combustion engine of the motor vehicle and provides the desired/permitted torque. In this case, the individual secondary units independently report their respective torque demands that are to be expected.
German Patent documents DE 102 32 354 A1 and DE 198 38 333 A1 describe such systems for controlling the drive of a vehicle where torque demands of main assemblies and secondary units are coordinated and, in which case, a desired actual torque of the drive unit is not influenced by reserve torque demands of external consuming devices and/or secondary units because torque demands or reserve torque demands are correspondingly limited. External consuming devices are, for example, electric consuming devices, such as car radios, electric sliding roofs, etc.; secondary units may, for example, be an air-conditioning compressor, a servo-motor, etc. The absolute reserve torque demands may also be a result of engine functions, such as the idle control.
These systems have in common that torque demands of external consuming devices and/or of secondary units are rejected when necessary so as to satisfy a torque desired by the driver and defined by the driver of the vehicle by operating an accelerator. Since the individual secondary units take over self-sufficient tasks, the demand for a torque of a secondary unit may take place at an unfavorable point in time; thus, for example, at an operating point of the engine which is unfavorable with respect to the efficiency or with respect to the available maximal torque, whereby a rejection of the demand is triggered. In the practical case of a torque demand by the air-conditioning compressor of an air-conditioning system, this means, for example, that no cooling output can be provided at an unfavorable point in time. An operating condition in which the torque change is very sensitive with respect to driving dynamics and can be noticed by the occupant in an unintended/uncomfortable manner is also considered to be unfavorable.
It is, therefore, an object of the invention to provide an alternative system for actuating at least one secondary unit that can be driven by a principal unit of a motor vehicle, which system results in fewer losses of comfort.
According to the invention, this object is achieved by a control unit for coordinating the actuation of at least one secondary unit of a motor vehicle, which can be driven by a principal unit of the motor vehicle, whereby an acquisition unit acquires limit values for the actuation of at least one secondary unit and an actual value from resources of the at least one secondary unit, and a decision unit controls the actuating of the at least one secondary unit as a function of its limit values and its actual value.
Furthermore, this object is achieved according to the invention by a process for coordinating the actuating of at least one secondary unit of a motor vehicle which can be driven by a principal unit of the motor vehicle, by
a) acquiring limit values for the actuating of at least one secondary unit and an actual value from resources of at least one secondary unit, and
b) controlling the actuating of the at least one secondary unit as a function of its limit values and its actual value.
Finally, this object is achieved according to the invention by a secondary unit of a motor vehicle which can be driven by a principal unit of the motor vehicle. An acquisition unit is provided for acquiring an actual value of a reserve from resources of the secondary unit.
Such a system for coordinating the actuation of at least one secondary unit of a motor vehicle, which can be driven by a principal unit of the motor vehicle, permits the optimal use of torque demands of the secondary unit as a function of the driving condition and simultaneously their reduced rejection because, for actuating a secondary unit, thus the switching-on by way of a defined or definable torque demand or the switching-off, takes place as a function of its resources, so that a storage device of the secondary unit, can, for example, already be replenished before it is absolutely necessary to switch on the secondary unit, therefore before the secondary unit would make a demand request. Not only absolute resources, such as the charge condition of a battery, are considered resources here but also resource reserves, such as a relationship between the charging condition of the battery and an actual power consumption or a predicted power demand.
The limit values of a secondary unit preferably are:
a mandatory value, starting at which the secondary unit has to be switched on when the actual value falls below this mandatory value;
an optional value, which is above the mandatory value, and starting at which the secondary unit may be switched on or off when the actual value falls below this optional value; and
a max value, which is greater than or equal to the optional value of the secondary unit, and starting at which the secondary unit should be switched off when the actual value reaches this max value.
In Step (b) noted above, the process according to the invention correspondingly performs such that:
a secondary unit is switched on when its actual value falls below a mandatory value of the secondary unit,
a secondary unit may be switched on or off when its actual value falls below an optional value of the secondary unit situated above the mandatory value of the secondary unit, and
a secondary unit is switched off when its actual value reaches a max value of the secondary unit which is greater than or equal to the optional value of the secondary unit.
As a result of such a division of limit values of the secondary unit, a range is created which is situated between the mandatory value and the optional value, and in which the secondary unit may be actuated but does not need to be actuated, thus, does not need to be driven by the principal unit of the motor vehicle in order to carry out its function. In the case of an air-conditioning system, this means, for example, that cooling output can still be obtained without requiring the air-conditioning compressor to run. Only when there is a falling below the mandatory value, will the secondary unit no longer be able to carry out its function without a supply of torque. According to the invention, an allocation of torque is therefore not only considered when the secondary unit absolutely needs it, but already starting in a condition in which it makes sense for replenishing resources of the secondary unit. According to the invention, the limit values are individually adjustable for each secondary unit. As an alternative, fixed limits can be set for all secondary units and an individual scaling of the actual value can be provided for each secondary unit.
It is also contemplated that the mandatory value is below a min value, which indicates the minimal resources of the secondary unit, whereby it is indicated that the corresponding secondary unit does not necessarily need to be switched on. In contrast to the generator/battery combination as a secondary unit, this makes sense, for example, in the case of the air-conditioning system as a secondary unit, whereby the latter can be switched off at the expense of the comfort and in favor of the handling characteristics; whereas the battery absolutely does have to be charged starting at a certain mandatory value situated above the discharged condition so that the battery will not be damaged.
Preferably, limit values and actual values of several secondary units are acquired according to the invention (by the acquisition unit) and the actuating of all acquired secondary units is controlled (by the decision unit).
Here, a respective individual controlling of the secondary units or a coordinated controlling of the secondary units can take place, preferably a prioritization of secondary units taking place corresponding to a priority, which is implemented, for example, as a function of a difference between the actual value and the mandatory value of the secondary unit. Such a prioritization has the effect that, when an actual value is between the mandatory value and the optional value of a secondary unit, those secondary units can be operated whose priority is high, and those secondary units can be switched off whose priority is low. The limit between a switching-on and a switching-off of a secondary unit preferably is variable. In addition, it can be defined in a particularly simple manner how much torque is provided to a secondary unit.
Preferably, the condition of the principal unit is acquired according to the invention (by the acquisition unit), and the actuating of the at least one secondary unit is controlled (by the decision unit) corresponding to the condition of the principal unit.
By this embodiment according to the invention, reserves can be formed in the secondary units when the principal unit is not fully utilized, particularly in the case of a demand by the secondary units to be expected. Furthermore, particularly as a result of the combination with a coordinated control of all queried secondary units, an optimal utilization of the principal unit becomes possible with an optimal storage of the resources of the secondary units, whereby a rejection of torque demands of secondary units is almost excluded.
According to the invention, the acquisition unit acquires the actual value of the at least one secondary unit, preferably from a demand buffer and/or limit values of the at least one secondary unit from a limit value memory. Such a demand buffer as well as such a limit value memory are preferably arranged in the corresponding secondary unit; however an arrangement can also take place centrally in a motor vehicle, for example, also in the control unit according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.